Conventional data backup systems can be relatively inefficient in the manner in which data is copied. Using such systems can in many cases result in a large amount of duplicate data, or blocks of data, being copied. It is typical for computers to back up many versions of the same document, with only slight variations between the versions. For example, if data from a computer system is routinely copied on a weekly basis to backup media, from week to week only a relatively small amount of data may be new. Unfortunately, in conventional backup systems, both the unchanged data and the new data are copied, which results in a significant amount of unnecessary, redundant data on the backup media.
To illustrate, after one week, all of the data that is backed up is considered unique. If 10% of the data changes from week to week, then after week two, only 55% of the total data will be unique. After week three, only 40% of the total data that is backed up is unique, and so on. After one year, less than 12% of the total data that is backed up is unique. As a result, greater storage capacity is required resulting in increased storage costs. Further, this redundancy of data being stored can cause an increase in data retrieval time from backup, decreasing the overall efficiency of the system.